Apparatus for conducting sound



P 1937. D. s. SPENS STEUART 2,992,423

APPARATUS FOR CONDUCTING SOUND Filed NOV. '29, L935 AW jaws 1M JM Q M mPatented Sept. 7, 1937 UNITED STATES PATENT OFFICE Application November29, 1935, Serial No. 52,256 In Great Britain December 10, 1934 20Claims.

The present invention relates to improvements in or relating to thetransmission and reception of sound waves and more particularly concernsimprovements in the surfaces which the sound waves pass or are reflectedby in the course of their passage from one part of an acoustic device toanother. The invention may be applied to loudspeakers, mouthpieces fortransmitters, speaking tubes or the like. Previously it has been foundthat the most satisfactory surface to be employed for reflecting soundwaves is obtained by utilizing an alloy of copper and zinc and whilealuminium has been tried it has been found to be particularlyunsatisfactory.

According to the invention aluminium suitably treated so as to have anoxide surface is utilized for the purpose of forming the surfaces ofmouthpieces, sound tubes, earpieces, diaphragms, and the likehereinafter referred to generally as sound conducting apparatus.

It has been found that aluminium mouthpieces when treated by what isknown as the anodizing process give superior results to those employingthe usual copper/zinc alloy, but the invention is not limited to thisparticular process as other known methods of producing a similar oxidesurface can be employed without departing from the spirit of theinvention. The invention is particularly suitable for use in connectionwith deaf aid instruments as it enables the weight of the device to beused in connection with the ear to be reduced very considerably.

In order that the invention may readily be understood an example ofsound conducting apparatus to which the invention may be applied willnow be described with reference to the accompanying drawing wherein Fig.l is a sectional view of a sound conducting apparatus, and

Fig. 2 is a plan view thereof.

The apparatus shown which corresponds to that illustrated in Figs. 9 and10 of my application filed of even date herewith, now Patent No.2,087,052, has an outer shell-like member formed. of aluminium oraluminium alloy or having an inner layer of aluminium or aluminiumalloy. This member is composed of a series of cylindrical Shell portionsAKBL, CMDN, EOFP and GQHR. each of successively smaller diameter. Theseportions are arranged co-axially in suitably spaced relationship. Thelargest diameter portion AKBL is joined at one end to one end of thenext smaller diameter portion CMDN by a frusto-conical shellportionBLCMwhile the cylindrical shell portion CMDN is joined at itsother end to one end of the next smaller portion still, namely, EOFP bythe frusto-conical shell portion DNEO. Similarly the cylindrical shellportion EOFP is joined by the frusto-conical shell portion FPGQ to thesmallest cylindrical shell portion GQHR. In this manner the outershell-like member is arranged to have cylindrical shell portionsalternating with portions shaped like the surface of a frustum of a coneso as to form a passage having a small opening at one end and a largeopening at the other.

The inner surface of the aluminium or aluminium alloy wall of the outershell like member is according to the invention treated in such a way asto have a much harder consistency than that of pure aluminium or thealloy for instance by anodical treatment or by a known chemical processso as to produce a coating 1 having a high degree of adherence andconsiderable hardness.

Arranged within the outer shell-like member are one or more membersformed of aluminium or aluminium alloy or at least on their outersurface facing the sound passage and having conical surfaces. One ofthese members is shown at STUV and has the shape of two equal conicalshells placed base to base, the apices being S and V and the common baseplane designated by TU. The plane TU is arranged to coincide with thatof the junction of the cylindrical portion AKBL with the frusto-conicalpart BLCM,

while the axial line of the double cone member is arranged coincidentWith that of the outer member.

The outer aluminium or aluminium alloy surfaces of the double conemember are coated by anodic or like treatment as previously describedand act as sound reflecting means, the upper cone in conjunction withthe cylindrical portion AKBL forming a passage of uniformly varyingcrosssection while the lower cone in conjunction with the frusto-conicalpart BLCM serves to reflect sound from one opening towards the other.

A similar double cone shaped member WXYZ is arranged at the junctionplane of the cylindrical portion EOFP with the frusto-conical part FPGQand operates in a similar manner to that just described.

The above described apparatus is merely by Way of example and theinvention is applicable to sound conducting tubes or reflectorsgenerally f and particularly to the devices illustrated and claimed inmy co-pending application of even date, above mentioned.

In sound conducting tubes the effect of the hardened surface is thatsound is transmitted vmetals can thus be avoided.

with a minimum of loss; in fact it has been generally recognized thataluminium although advantageous on account of its lightness could not besatisfactorily employed whereas with the method according to theinvention very satisfactory results are obtained and the use of heavierActually I have found that pure aluminium gives the most satisfactoryresults but as improved results are also obtained with aluminium alloysthese must be considered as included within the scope of my invention.

In sound reflecting apparatus, the hardness of the surface employedaccording to the invention also gives very efficient results so that inan apparatus such as illustrated both advantages are made use of andwhen such apparatus is used as a mouthpiece very satisfactory resultsare obtained, speech uttered at a distance of two feet is capable ofbeing reproduced with considerable loudness and with a remarkablefreedom from distortion which is prevalent in other forms of mouthpiece.

The various parts of the apparatus as described above are preferablyconstructed by means of spinning, in which case the outer member can beconstructed in one piece while the double cone members are each arrangedas a two-piece construction the upper cones being formed integral withtubular extensions 2. which are adapted to fit and be secured within thenext smaller cylindrical portion of the outer member.

Several large portions of each of the tubular extensions 6 lying betweenthe base plane of the double cone member and the supporting cylindricalportion of the outer member are cut away so as to leave only narrowsupporting arms s.

It should be pointed out that by processes involving the anodictreatment of aluminium and its alloys coatings of varying degrees ofresistance and hardness may be produced. The coatings which come intoquestion in the present invention are those characterized by a highdegree of adherence and considerable hardening, i. e. a hardeningmaterially greater than that of aluminium or aluminium alloy itself.Such coatings may also be produced on aluminium and its alloys by purelychemical methods.

The treatment of the surfaces as described may be efi'ected eitherbefore or after the assembly of the parts While the exterior surfacesmay also be similarly treated if desired.

I claim:

1. Sound conducting apparatus formed of aluminium-containing metal whichis provided with a hard superficial layer produced by processesinvolving anodic treatment.

2. Sound conducting apparatus formed of metal mainly consisting ofaluminium which is provided with a hard superficial layer produced byprocesses involving anodic treatment.

3. Sound conducting apparatus formed of substantially pure aluminiumwhich is provided with a hard superficial layer produced by processesinvolving anodic treatment.

4. Sound conducting apparatus formed of metal mainly consisting ofaluminium which is anodically treated so as to offer a hard surfacefacing the sound passage.

5. Sound conducting apparatus formed of substantially pure aluminiumwhich is anodically treated so as to offer a hard surface facing thesound passage.

6. Sound conducting apparatus having sound reflecting members formed ofaluminium-containing metal which is provided with a hard superficiallayer produced by processes involving anodic treatment.

7. Sound conducting apparatus having sound reflecting members formed ofmetal mainly consisting of aluminium which is anodically treated so asto offer a hard surface facing its sound passage.

8. Sound conducting apparatus having walls embracing a passage formed ofaluminium-containing metal the surface of the lining facing the soundpassage being provided with a. hard superficial layer produced byprocesses involving anodic treatment.

9. Sound conducting apparatus having walls embracing a passage formed ofmetal mainly consisting of aluminium the surface of the lining facingthe sound passage being provided with a hard coating by anodictreatment.

10. Sound conducting apparatus having cylindrical walls formed ofaluminium-containing metal which is provided with a hard superficiallayer produced by processes involving anodic treatment on the innersurface.

11. Sound conducting apparatus having cylindrical Walls formed ofsubstantially pure aluminium anodically treated on the inner surface.

12. Sound conducting apparatus having a Wall shaped like the surface ofa conical frustum and formed of aluminium-containing metal which isprovided with a hard superficial layer produced by processes involvinganodic treatment on the inner surface.

13. Sound conducting apparatus having an outer wall shaped like acylindrical surface and formed of metal mainly consisting of aluminiumwhich is provided with a hard layer by anodic treatment on its innersurface and an inner wall shaped like the surface of a cone and formedof metal mainly consisting of aluminium which is provided with a hardlayer by anodic treatment on its outer surface, the two walls forming apassage of uniformly varying cross section.

14. Sound conducting apparatus having an outer wall shaped like afrustum of a cone and formed of metal mainly consisting of aluminiumwhich is anodically treated so as to provide a hard layer on its innersurface and an inner wall shaped like the surface of a cone and formedof metal mainly consisting of aluminium which is anodically treated soas to provide a hard layer on its outer surface, the two surfacesforming a passage by which sound may be reflected from one surface tothe other.

15. Sound conducting apparatus comprising a spinning of metal mainlyconsisting of aluminium anodically treated so as to provide a hard layeron its inner surface and arranged to have cylindrical portionsalternating with portions shaped like the surface of the frustum of acone so as to form a passage having a small opening at one end and alarge opening at the other end.

16. Sound conducting apparatus comprising a spinning of substantiallypure aluminium anodically treated so as to provide a hard layer on itsinner surface and arranged to have cylindrical portions alternating withportions each shaped like a frustum of a cone so as to form a passagehaving a small opening at one end and a large opening at the other endone or more members shaped like the surface of a cone also formed ofsubstantially pure aluminium anodically treated so as to provide a hardlayer on the outer surface and spaced centrally in said spinning for thepurpose of reflecting sound in conjunction with the frustum shapedportions from one end opening towards the other.

17. Sound conducting apparatus formed of a metal alloy comprisingaluminium which is provided with a hard superficial layer consisting ofan aluminium compound.

18. Sound conducting apparatus formed of substantially pure aluminiumwhich is provided with a hard superficial layer consisting of an alumin-10 ium compound.

reflecting members formed of a metal alloy comprising aluminium which isprovided with a hard superficial layer consisting of an aluminiumcompound.

20. Sound conducting apparatus having walls embracing a passage formedof a metal alloy comprising aluminium the surface of the lining facingthe sound passage being provided with a hard superficial layerconsisting of an aluminium compound.

DOUGLAS STUART SPENS STE'UART.

